1. Field of the Invention
The present invention relates to a bead core of pneumatic tires in which loosening of a bead wire is prevented by means of staple fittings.
2. Background of the Invention
Bead cores for pneumatic tires of so-called single wind structure are being heavily used in which a single bead wire is successively wound in a multi-seriate and multi-staged manner. In case of a bead core of such a structure, the bead core is generally solidified by wrapping the entire bead core by means of a wrapping sheet made of textile cloth or similar for preventing loosening of the wound and overlapped bead wire and for maintaining its shape at cross-sectional surface thereof. However, such wrapping using a wrapping sheet is inferior in terms of operating efficiency, and it may cause degradations in productivity or higher expenses.
It is thus being performed in these years that a C-shaped staple fitting (a) made of a metallic wire rod is employed as illustrated, for instance, in FIG. 8(A), for surrounding the periphery of the bead core (b) to be solidified at several spots including at least the start portion and the end portion of winding.
However, while such a staple fitting (a) is capable of preventing loosening, the clamping force to the bead core (b) is weak. Accordingly, the staple fitting (a) tends to be pulled by a carcass (c) to cause a positional shift in a rotating direction around the bead core as illustrated in FIG. 8(B) during shaping when forming a green tire. As a result, a tip end al of the staple fitting (a) will project through carcass cords into a tire cavity side so that a drawback of damaging an inner liner rubber is caused.